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Summary: New NASA imagery of the Vesta asteroid appears to show a very large landslide. The challenge is to find a good terrestrial analogue to this slip.

The NASA Dawn mission is currently imaging using a range of instrumentation to image the Vesta asteroid. A few days ago they released this fascinating image of the South Polar region, showing a huge “mountain” . This feature is 22 km high – about three times the height of Everest. Note the strange topographic features around it, but note also that the image is exaggerated vertically by about 50% and has had the underlying topographic curvature (the same effect as the curvature of the Earth) removed.

Whilst the image itself is really interesting, for me the most fascinating aspect is the tall ridge on the right side, shown enlarged here:

The NASA hypothesise that the deposits at the toe of this scarp, especially on the centre right I suspect, are those from very large landslides. I suspect from the morphology that this is correct. In the image below I have highlighted in black the main block that I would interpret as being a landslide (note the boundaries are indicative at best):

The area that I have high;lighted in red appears to be a small secondary slip in the landslide mass. It is interesting that the very large main landslide complex appears to have slipped but not to have spread in the way that the Saidmareh landslide appears to have:

I have been trying to think of a terrestrial analogue. So far the best I can come up with is the Quiraing on the Isle of Skye, but this is not really a good analogue overall.

http://www.panoramio.com/photo/43503956

There must be much better examples, so over to you. I’ll try to post the best suggestions here over the next few days.

As noticed above for the Vesta Asteroid landslide, the observation of the black and white picture would suggest that the deposits did not spread and the accumulation area is located just downstream of the main scarp.

As a 10yo kid I visited the Hope Slide from 1965 shortly after a road was pushed through the debris field. The fascinating observation to me was how the debris from the slide had apparently sloshed 1-200m up the opposing mountain slopes, then back and forth down the valley several miles. The path of the flow was obvious from the complete denudation of vegetation, in this case a rain forest with some hefty trees. It was the first time I realized that rock could act like a fluid given the gradation and compression characteristics were suitable.

I wonder to what extent you can expect to find a similar slide on Earth. Given the low gravity at the surface of Vesta (just 2% that of the earth) I would expect very low acceleration of the slide material, giving the slide very little momentum and a low velocity. That would easily explain why the mass did not spread. Do landslides on earth ever happen at such a low velocity?

A larger earth landslide simular to Vesta, which I just heard about, is the underwater landslide to the north of the Hawaian island Molokai. Evidently half the island collapsed. I saw this on the Science Channel… USA television, about 3-4 months back.

[…] space rock earlier this year. The topography of the scarp and its surroundings indicates that huge landslides may have occurred down this slope. The scarp’s origin remains unknown, but parts of the […]

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About Dave

Dave Petley is the Pro-Vice-Chancellor (Research and Innovation) at the University of Sheffield in the United Kingdom. His blog provides a commentary on landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.

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